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1 Nam e Index N um ber 233/2 Candidate s Signature CHEMISTRY Paper 2 Date... Nov hours THE KENYA NATIONAL EXAMINATIONS COUNCIL Kenya Certificate of Secondary Education CHEMISTRY Paper 2 (THEORY) 2 hours Instructions to candidates (a) Write yo u r nam e and index num ber in the spaces provided above. (b) Sign and w rite the date o f exam ination in the spaces provided above. (c) A nsw er all the questions in the spaces provided. (d) K N E C m athem atical tables and silent non-program m able electronic calculators m ay be used. (e) All w orking must be clearly show n w here necessaty. ( f) This paper consists of 12 printed pages. (g) Candidates should check the question paper to ascertain that all the pages are printed as indicated and that no questions are missing. (h) Candidates should answer the questions in English. Question For Examiner s Use Only Maximum Score Total Score 80 Candidate s Score Q1 f.s C \A 2016 The Kenya National Examinations Council

2 Use the information in the table below to answer the questions that follow. The letters do not represent the actual symbols of the elements. Element Atomic number Melting point C R S T U (a) (b) V W Give a reason why the melting point of: (i) S is higher than that of R. (ii) V is lower than that of U. How does the reactivity of W with chlorine compare with that of R with chlorine? (c) Write an equation for the reaction between T and excess oxygen. (1 mark)

3 Kenya Certificate of Secondary Education, 2016 ou^ n/i???/? Turn over 3 (d) When 1.15 g of R was reacted with water 600 cm3of gas was produced. Determine the relative atomic mass of R. (Molar gas volume = cm3) (3 marks) (e) Give one use of element V. (1 mark) 2. (a) Describe the process by which nitrogen is obtained from air on a large scale. (4 marks) (b) Study the flow chart below and answer the questions that follow.

4 4 (i) Identify gas J. (1 mark) (ii) Using oxidation numbers show that ammonia is the reducing agent in step (VI) (c) (iii) Write the equation for the reaction that occurs in step (V). (1 mark) (iv) Give two uses of ammonia nitrate. The table below shows the observation made when aqueous ammonia was added to cation of elements E, F and G until in excess. Cation of Addition of a few drops of aqueous ammonia E White precipitate Insoluble Addition of excess aqueous ammonia F No precipitate No precipitate G White precipitate Dissolves (i) Select the cation that is likely to be Zn2+. (1 mark) (ii) Given that the formula of the cation of element E is E2+ write the ionic equation for the reaction between E2+ (aq) and aqueous ammonia. (1 mark) Kenya Certificate o f Secondary Education, 2016

5 5 3. (a) Methanol is manufactured from carbon (IV) oxide and hydrogen gas according to the equation. C0:,g, + 3H2(g) CH OH. + H (g) 2 (g) The reaction is carried out in the presence of a chromium catalyst at 700K and 300k pa. Under these conditions, equilibrium is reached when 2% of the carbon (IV) oxide is converted to methanol. (i) How does the rate of the forward reaction compare with that of the reverse reaction when 2% of the carbon (IV) oxide is converted to methanol? (1 mark) (ii) Explain how each of the following would affect the yield of methanol: I reduction in pressure II using more efficient catalyst (iii) If the reaction is carried out at 500k and 300k pa, the percentage of carbon (IV) oxide converted to methanol is higher than 2%. I What is the sign of AH for the reaction? Give a reason q i f i s r u Kenya Certificate of Secondary Education, /2 Turn over

6 6 II Explain why in practice the reaction is carried out at 700K but not at 500K (b) Hydrogen peroxide decomposes according to the following equation: 2H20 2 (aq) >2H20(I) + 0 2(g) In an experiment the rate of decomposition of hydrogen peroxide was found to be 6.0 X 10~8 moldm 3S_1 (i) (ii) Calculate the number of moles per dm3of hydrogen peroxide that has decomposed within the first 2 minutes. In another experiment, the rate of decomposition was found to be 1.8 X 10~7moldm 3S H. The difference in the two rates could have been caused by addition of a catalyst. State giving reason, one other factor that may have caused the difference in the two rates of decomposition. Kenya Certificate o f Secondary Education, 2016

7 7 4. (a) The set up below can be used to produce sodium hydroxide by electrolysing brine. Y Hydrogen (ii) (iii) (1 mark) Describe how aqueous sodium hydroxide is formed in the above set-up. One of the uses of sodium hydroxide is in the manufacture of soaps. State one other use of sodium hydroxide. (1 mark) (b) Study the information given below and answer the questions that follow Half reactions Electrode potential E QV D 2(aq) + 2e ~ + D <» E(aq) + e ~ F ( a q ) + e G(aq) 2 e H(aq) + 2e (s) J (a q ) + e ~ + J n <s) f t l C A /1 Kenya Certificate o f Secondary Education, 2016 m n Turn over

Kottxm ('ortifirnip n f Secondary Education. 2016 8 (i) Construct an electrochemical cell that will produce the largest e.m.f. (3 marks) (ii) Calculate the e.m.f. of the cell constructed in (i) above.

8 Kottxm ('ortifirnip n f Secondary Education (i) Construct an electrochemical cell that will produce the largest e.m.f. (3 marks) (ii) Calculate the e.m.f. of the cell constructed in (i) above. (iii) Why is it not advisable to store a solution containing E+ ions in a container made of H? 5. The diagram below represents a set up of an electrolytic cell that can be used in the production of aluminium. Molten aluminium Molten aluminium oxide and cryolite

9 9 (a) On the diagram, label the anode. (1 mark) (b) Write the equation for the reaction at the anode. (1 mark) (c) Give a reason why the electrolyte process is not carried out below 950 C. (1 mark) (d) Give a reason why the production of aluminium is not carried out using reduction process. (1 mark) (e) Give two reasons why only the aluminium ions are discharged. (f) State two properties of duralumin that makes it suitable for use in aircraft industry. (g) Name two environmental effects caused by extraction of aluminium Kenya Certificate o f Secondary Education, /2 Turn over

10 (a) Draw the structural formula for all the isomers of C2H3C13. (b) (c) Describe two chemical tests that can be used to distinguish between ethene and ethane. (4 marks) The following scheme represents various reactions starting with propan-l-ol. Use it to answer the questions that follow. carbonate (i) Name one substance that can be used in Step I. (1 mark) (ii) Give the general formula of X. (1 mark) Coriifirntp nf Secondary Education, 2016

11 11 (iii) Write the equation for the reaction in Step IV. (1 mark) (iv) Calculate the mass of propan-l-ol which when burnt completely in air at room temperature and pressure would produce 18dm3of gas. (C = 12.0, O = 16.0, H = 1.0; molar gas volume = 24dm3) (3 marks) 7. (a) Write an equation to show the effects of heat on the nitrates of: lil Potassium (1 mark) (ii) Silver (1 mark) (b) The table below gives information about elements A1? A2, A3and A4. Elements Atomic Number Atomic radius (nm) A A A A Atomic radius (nm) Q16S04 Kenya Certificate of Secondary Education, /2 Turn over

12 1 2 (i) In which period of the periodic table is element A2? Give a reason. (ii) Explain why the atomic radius of: I A1 is greater than that of A2 II A1 is smaller than its ionic radius. (iii) Select the element which is in the same group as A3. (1 mark) (iv) Using Dots (.) and crosses (x) to represent outermost electrons, draw a diagram to show the bonding in the compound formed when A1 reacts with A4. THIS IS THE LAST PRINTED PAGE. Kenya Certificate o f Secondary Education, 2016

CHEMISTRY PAPER 2. Element Atomic Number. Meltrng Point CC) R S T U V

CHEMISTRY PAPER 2. Element Atomic Number. Meltrng Point CC) R S T U V CHEMISTRY PAPER 2 No. 1. Use the information in the table below to answer the questions that follow. The letters do not represent the actual symbols of the elements. Element Atomic Number Meltrng Point